A continuous system for recovering triethylamine hydrochloride with calcium oxide

Abstract

The application discloses a continuous system for recovering triethylamine hydrochloride by adopting calcium oxide, relates to the technical field of organic amine recovery, and aims to solve the problems of low reaction efficiency, high energy consumption caused by unrecycled latent heat at the top of a tower and easy plugging of a tower kettle in the prior art. The device comprises a triethylamine hydrochloride preparation kettle, a calcium oxide pulping kettle, a static mixer, a neutralization liquid intermediate tank and a rectifying tower. The static mixer is provided with a jacket, the jacket heat medium inlet is connected with the gas phase outlet at the top of the rectifying tower, and the feed is preheated by using the steam at the top of the tower. The tower kettle of the rectifying tower is provided with a forced circulation pump and an online self-cleaning filter, which are used for preventing salt particles from depositing. The continuous reaction of the static mixer and the anti-blocking and energy-saving design of the rectifying tower are adopted, so that the efficient recovery of triethylamine is realized, and the continuous industrial recovery of triethylamine in the glyphosate production process can be realized.

Description

Technical Field

[0001] This invention relates to the field of organic amine recovery technology, and more specifically to a continuous system for recovering triethylamine hydrochloride using calcium oxide. Background Technology

[0002] Glyphosate is the most widely used non-selective herbicide globally. The glycine process, with its mature technology and suitability for industrial-scale production, has become the mainstream process for glyphosate production. However, the production process generates a mother liquor containing triethylamine hydrochloride, which needs to be recovered and recycled back to the synthesis stage. Currently, the existing technology mainly faces the following technical problems:

[0003] I. Intermittent operation leads to low production efficiency. Existing technologies mostly use solid NaOH dehydration to recover triethylamine, which requires manual addition of solid NaOH for dehydration. The operation is intermittent, which is not only labor-intensive but also extremely inefficient, and cannot meet the needs of large-scale continuous production.

[0004] II. Large quantities of sodium chloride are produced as a byproduct, making treatment difficult. Some existing processes use liquid alkali (sodium hydroxide solution) to neutralize and recover triethylamine hydrochloride from the mother liquor. This introduces sodium ions, resulting in a large amount of industrial sodium chloride as a byproduct. According to material balance calculations, producing 1 ton of glyphosate will produce approximately 0.778 tons of sodium chloride as a byproduct. Currently, the industry typically treats the byproduct salt by selling it externally, using it in the chlor-alkali industry, or through membrane treatment. However, these are all stopgap measures that do not address the root cause and can easily have a significant environmental impact or consume large amounts of energy.

[0005] 3. The equipment is prone to clogging and cannot operate for extended periods. In existing recycling processes, neutralization reactions are mostly carried out in traditional stirred tanks, which are intermittent reactions. Furthermore, the materials are not mixed evenly during the reaction, resulting in low reaction efficiency. At the same time, high-concentration calcium chloride or sodium chloride mother liquor easily precipitates solid impurities during subsequent distillation, leading to frequent equipment blockages and forced shutdowns for cleaning, severely impacting production continuity.

[0006] IV. Low energy utilization rate and high overall energy consumption In traditional distillation recovery processes, the latent heat of high-temperature vapor generated at the top of the column is usually directly discharged or carried away by condensate, failing to be effectively recovered and utilized. This results in high overall energy consumption of the entire system, increasing the operating costs of production enterprises, and failing to achieve energy cascade utilization. Summary of the Invention

[0007] To address the aforementioned deficiencies in existing technologies, this invention provides a novel continuous system for recovering triethylamine hydrochloride using calcium oxide, thereby solving the problems of large amounts of sodium chloride byproduct, low production efficiency, high energy consumption, and easy equipment blockage in existing technologies.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A continuous system for recovering triethylamine hydrochloride using calcium oxide includes: Triethylamine hydrochloride preparation vessel, used to prepare a solution of triethylamine hydrochloride with water; A calcium oxide slurry preparation vessel is used to prepare a slurry from calcium oxide and water. A static mixer is provided with two mixing chambers and an external jacket. The two inlets of the static mixer are respectively connected to the triethylamine hydrochloride preparation vessel and the calcium oxide slurry preparation vessel via a delivery pump. This is used to allow the solution and slurry to undergo a neutralization reaction in the first mixing chamber and to deeply release triethylamine in the second mixing chamber. The neutralization liquid intermediate tank is connected to the outlet of the static mixer; A distillation column, the inlet of which is connected to the outlet of the neutralized liquid intermediate tank; A reboiler, connected to the bottom of the distillation column, is used to provide heat load; A forced circulation pump has its inlet connected to the bottom of the distillation column bottom and its outlet divided into two paths: one path returns to the distillation column bottom inlet to form a high-speed flushing circulation, and the other path connects to the calcium chloride mother liquor storage tank. An online self-cleaning filter is installed on the circulation pipeline of the forced circulation pump to remove precipitated salt particles in real time; A vapor phase condenser is connected to the vapor phase outlet at the top of the distillation column; The reflux tank is connected to the condensate outlet of the vapor phase condenser, its reflux port is connected to the top of the distillation column, and its outlet is connected to the crude triethylamine storage tank. The external jacket of the static mixer has a heat medium inlet connected to the top vapor outlet of the distillation column, which is used to preheat the feed using the top vapor.

[0009] Furthermore, the first-stage mixing chamber of the static mixer is equipped with a pH detection port, and the pH value of the material after reaction is maintained at 9-11 by adjusting the flow rate of the feed pump.

[0010] Furthermore, the distillation column is equipped with an anti-clogging guide valve tray, the tray having an opening ratio of ≥12%, and is equipped with an anti-dead zone structure.

[0011] Furthermore, the distillation column operates under atmospheric pressure, with the bottom temperature controlled at 100-110℃ and the top temperature controlled at 90-100℃.

[0012] Furthermore, it also includes a DCS control system. Temperature sensors and pH sensors are installed at the triethylamine hydrochloride preparation vessel, the outlet of the static mixer, and the bottom of the distillation column. The DCS control system automatically regulates each delivery pump and valve based on the sensor signals.

[0013] Furthermore, the calcium oxide slurry preparation vessel is equipped with an airflow conveying device for conveying calcium oxide powder into the vessel in a sealed manner.

[0014] Furthermore, a basket filter is installed on the inlet pipe of the calcium chloride mother liquor storage tank for filtering the extracted calcium chloride mother liquor.

[0015] Furthermore, the gas phase condenser uses circulating water as the refrigerant to condense the gas phase into a liquid.

[0016] Furthermore, the outlet of the forced circulation pump is divided into two paths: one path returns to the bottom inlet of the distillation column, and the other path connects to the calcium chloride mother liquor storage tank.

[0017] Furthermore, a filter is installed on the outlet pipeline from the bottom of the distillation column to the calcium chloride mother liquor storage tank to intercept solid impurities in the calcium chloride mother liquor.

[0018] Beneficial effects 1. Continuous reaction and efficient mixing effect By replacing the traditional stirred tank with a two-stage static mixer, not only can the neutralization reaction and the deep ionization reaction be carried out continuously, greatly improving production efficiency, but the static mixer also has no mechanical seal components, resulting in low maintenance costs. The reactants are forcibly cut and mixed in the pipeline, and the reaction rate and conversion rate are much higher than those of the traditional stirred tank, effectively ensuring the thoroughness of the reaction.

[0019] 2. Energy-saving effect of thermal coupling This invention ingeniously connects the vapor outlet at the top of the distillation column to the external jacket of a static mixer, utilizing the latent heat of the vapor at the top of the column to preheat the cold feed (triethylamine hydrochloride solution and calcium oxide slurry) entering the static mixer. This unique energy cascade utilization path not only reduces external heating energy consumption but also lowers the refrigerant load on the vapor phase condenser, achieving a significant reduction in the overall system energy consumption.

[0020] 3. Anti-blocking and stable operation effect By installing a forced circulation pump in the reboiler of the distillation column, and combining it with an online self-cleaning filter on the circulation pipeline, continuous extraction, flushing, and filtration of the liquid phase in the reboiler are achieved. This combined structure effectively prevents high-boiling-point viscous substances and ammonium salt crystals from depositing on the inner wall of the reboiler and in the reboiler through high-speed flushing. At the same time, the self-cleaning filter removes precipitated particles in real time, greatly reducing the frequency of shutdown cleaning and significantly improving the system's continuous and stable operation capability.

[0021] 4. Environmental protection and value-added effects of by-products By using calcium oxide instead of liquid alkali as a neutralizing agent, the introduction of sodium ions is completely avoided. The calcium chloride mother liquor generated by the reaction can be directly used as a commercial raw material or further evaporated and crystallized for recovery, thus avoiding the generation of a large amount of industrial sodium chloride by-product. This has good environmental benefits and high economic added value of by-products. Attached Figure Description

[0022] Figure 1 This is a simplified flow chart of a continuous system for recovering triethylamine hydrochloride using calcium oxide, according to the present invention.

[0023] Figure labels: 1-Triethylamine hydrochloride preparation vessel; 2-Calcium oxide slurry preparation vessel; 3-Static mixer; 4-Neutralization liquid intermediate tank; 5-Distillation column; 6-Reboiler; 7-Forced circulation pump; 8-Online self-cleaning filter; 9-Vacuum phase condenser; 10-Reflux tank; 11-Crude triethylamine storage tank; 12-Calcium chloride mother liquor storage tank; 13-Basket filter. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the implementation of the present invention is not limited thereto.

[0025] This invention provides a continuous system for recovering triethylamine hydrochloride using calcium oxide, comprising: a raw material preparation unit, a reaction and preheating unit, a distillation and separation unit, and a post-processing and storage unit. The raw material preparation unit includes a triethylamine hydrochloride preparation vessel 1 and a calcium oxide slurry preparation vessel 2; the reaction and preheating unit includes a static mixer 3 with an external jacket and a neutralization intermediate tank 4; the distillation and separation unit includes a distillation column 5, a reboiler 6, a vapor-phase condenser 9, and a reflux tank 10; and the post-processing and storage unit includes a forced circulation pump 7, an online self-cleaning filter 8, a basket filter 13, a crude triethylamine storage tank 11, and a calcium chloride mother liquor storage tank 12. The jacketed heat medium inlet of the static mixer 3 is specifically connected to the vapor-phase outlet at the top of the distillation column 5 via a pipeline, forming a unique thermal coupling path for preheating the feed with top vapor. This overall design solves the problems of uneven material mixing, heat waste, and easy blockage of the column in the prior art, achieving significant technical effects of continuous operation, low energy consumption, and long-term operation.

[0026] As the initial step of the entire system, the triethylamine hydrochloride preparation vessel 1 is used to prepare a solution of triethylamine hydrochloride and water. In actual operation, the ratio of triethylamine hydrochloride to water can be selected from a range of values ​​such as 1:0.5, 1:1, 1:1.5, or 1:2. The basis for selecting this ratio is that if the amount of water is too large, it will lead to a significant increase in the heating load of the subsequent distillation column 5, reducing the unit capacity; if the amount of water is too small, the triethylamine hydrochloride may not be completely dissolved or the solution viscosity may be too high, affecting the subsequent pumping and mixing effect. Therefore, within the above ratio range, it can be ensured that a triethylamine hydrochloride aqueous solution with good fluidity and appropriate concentration is formed. At the same time, the calcium oxide slurry vessel 2 is used to prepare a slurry of calcium oxide and water. Calcium oxide powder is preferably conveyed to the slurry vessel 2 in a closed manner using an air pneumatic conveying device, and fully mixed under the action of stirring. The ratio of calcium oxide to water can be selected from a range of values ​​such as 1:1, 1:1.2, 1:1.5, or 1:1.8. The selection of this ratio is based on the following: if there is too little water, the slurry will be too viscous or even paste-like, making it impossible to pump; if there is too much water, the effective calcium oxide concentration in the slurry will be too low, resulting in excessive water being carried into the distillation column 5 and increasing energy consumption. This ratio range ensures that the slurry has appropriate fluidity and high reactivity, facilitating pump delivery and rapid reaction within the static mixer 3.

[0027] Subsequently, the triethylamine hydrochloride solution and calcium oxide slurry are transported to the static mixer 3 via a transfer pump (such as a centrifugal pump or screw pump, which can be flexibly selected according to the material viscosity). The static mixer 3 employs a two-stage mixing design: the first stage serves as a neutralization reaction chamber, and the second stage as a deep ionization chamber. It should be noted that the two-stage mixing chamber can be two independent static mixer units connected in series, or a combination of two mixing elements with different structures integrated within a single casing. As long as it functionally achieves the two-stage reaction of neutralization followed by deep ionization, it falls within the scope of this invention. During the mixing process, the pH value of the reaction solution must be strictly controlled between 9 and 11. The pH value is selected based on the following: if the pH value is below 9, the triethylamine hydrochloride cannot be completely ionized, leading to a decrease in recovery rate; if the pH value is above 11, there will be excessive free calcium oxide in the system, which not only wastes the alkali source but may also introduce more calcium ions, causing scaling in subsequent equipment. Furthermore, excessive alkalinity may trigger side reactions. Therefore, controlling the pH within the range of 9-11 ensures complete release of triethylamine while suppressing side reactions. Simultaneously, the heat medium inlet of the external jacket of the static mixer 3 is connected to the vapor outlet at the top of the distillation column 5 via a pipeline, utilizing the vapor from the top of the column to preheat the cold feed entering the static mixer 3. This feature effectively recovers the latent heat of the vapor from the top of the column, reducing the overall heating energy consumption of the system. Through this thermal coupling design, the vapor from the top of the column is partially condensed while preheating the feed, directly reducing the heat load on the subsequent vapor condenser 9. Furthermore, due to the increased feed temperature, the amount of live steam required by the reboiler 6 at the bottom of the distillation column 5 is correspondingly reduced, thus achieving a dual energy-saving effect for the system. The external jacket of the static mixer 3 can be a spiral jacket or a semi-pipe jacket, depending on actual needs, as long as a heat medium can be introduced for heat exchange; both are equivalent alternatives of this invention.

[0028] After the reaction is complete, the neutralized liquid enters the intermediate neutralized liquid tank 4 for buffering to balance the flow fluctuations between the preceding and following processes and ensure the stability of the feed to the subsequent distillation column 5. The intermediate tank enables the system to cope with potential instantaneous flow instability between the preceding and following processes, solving the problem of operational disorder in the distillation column 5 caused by feed fluctuations in existing technologies, and achieving stable operation.

[0029] The neutralized liquid is then pumped into the distillation column 5. The distillation column 5 preferably uses an anti-clogging guided floating valve tray with an open area ratio ≥12% and an anti-dead zone structure. This tray was chosen because ordinary trays are prone to clogging and dead zone accumulation due to the presence of calcium chloride and trace amounts of suspended solids in the system. The anti-clogging guided floating valve tray, combined with the anti-dead zone structure, effectively guides the flow of the gas and liquid phases, preventing solid impurities from accumulating in the dead zone of the tray. This solves the problem of easy clogging in traditional distillation columns 5 and ensures high efficiency of gas-liquid mass transfer within the column. The distillation column 5 operates under atmospheric pressure, with the bottom temperature controlled at 100-110℃ (e.g., 100℃, 105℃, 108℃, 110℃) and the top temperature at 90-100℃ (e.g., 90℃, 93℃, 97℃, 100℃). The temperature control is based on the following: triethylamine and water form an azeotrope under normal pressure. Maintaining the top temperature of the column at 90-100℃ ensures that the volatile light component triethylamine and some water are distilled off from the top of the column in gaseous form. Maintaining the bottom temperature of the column at 100-110℃ ensures that the triethylamine in the calcium chloride mother liquor in the bottom of the column is completely distilled off, while avoiding excessively high temperatures that could lead to accelerated calcium chloride crystallization. The synergistic effect of this temperature window achieves efficient volatilization and separation of triethylamine while suppressing side reactions.

[0030] A reboiler 6 is connected to the bottom of the distillation column 5. The reboiler 6 uses steam to provide the heat load, vaporizing part of the liquid phase in the column bottom and returning it to the column. Simultaneously, a forced circulation pump 7 is installed at the bottom of the column bottom to continuously extract the liquid phase. The outlet of the forced circulation pump 7 is divided into two paths: one path returns to the inlet of the distillation column 5 to form a high-speed flushing circulation, and the other path is drawn to the calcium chloride mother liquor storage tank 12. An online self-cleaning filter 8 is installed on the circulation pipeline of the forced circulation pump 7 to remove precipitated salt particles in real time. This combination of features (forced circulation + online filtration) is chosen because high-concentration calcium chloride mother liquor is prone to crystallization or carrying high-boiling-point organic matter that deposits at the bottom of the column bottom and in the reboiler 6 under high-temperature conditions. If not removed in time, it will lead to equipment blockage and shutdown. The high-speed flushing circulation prevents the formation of a stagnant zone at the bottom of the column bottom, and the deposits are re-entrained into the liquid phase and then removed in real time by the online self-cleaning filter 8. Therefore, this feature effectively solves the technical problem of frequent blockage in the bottom of distillation column 5 in the background technology, and significantly extends the cleaning cycle of the equipment. A filter is also installed on the outlet pipeline from the bottom of distillation column 5 to the calcium chloride mother liquor storage tank 12 to intercept solid impurities in the calcium chloride mother liquor and ensure that the outlet calcium chloride mother liquor is clear.

[0031] The vapor phase (containing triethylamine and water vapor) distilled from the top of distillation column 5 goes to the vapor phase condenser 9. The vapor phase condenser 9 preferably uses circulating water as the refrigerant to condense the vapor phase into a liquid phase. This choice is based on the fact that circulating water is widely available and inexpensive, meeting the process requirement of condensing the top vapor into liquid. The condensed liquid goes to the reflux tank 10; a portion is returned to the top of distillation column 5 as reflux liquid via a reflux pump, and the other portion goes to the crude triethylamine storage tank 11 as produced liquid. During this process, by adjusting the reflux ratio, crude triethylamine with a content of 90%-93% (moisture content controlled at 7%-10%) can be obtained. This purity control is based on the fact that this concentration of crude triethylamine fully meets the purity requirements for subsequent recycling to the glyphosate synthesis station, without the need for excessive purification, ensuring high recovery efficiency and low energy consumption costs. The high-boiling-point material in the bottom of distillation column 5 is calcium chloride mother liquor. The mother liquor is pumped from the bottom liquid outlet of the tower and filtered through a basket filter 13 (or a tubular filter if necessary) to remove mechanical impurities and fine suspended solids, ultimately yielding a calcium chloride mother liquor with a concentration of 21%-30%, which is then stored in the calcium chloride mother liquor storage tank 12. This concentration is based on the fact that calcium chloride mother liquor within this concentration range has good fluidity, allowing it to be sold directly as a crude product or used as a high-quality raw material for subsequent evaporation and crystallization processes, thus achieving high-value utilization of the byproduct.

[0032] Finally, all pumps, valves, temperature sensors, and pH sensors in the entire system are preferably connected to a DCS (Distributed Control System) for fully automated control of the entire process. The DCS control system can automatically adjust the flow rate of each pump and the steam intake of reboiler 6 according to the set temperature and pH value, ensuring stable operation of the system under optimal conditions. The realization of full-process automation greatly reduces operational errors caused by manual intervention, solves the problem of product quality fluctuations caused by reliance on manual operation in existing technologies, and achieves the beneficial effects of high automation and high stability.

[0033] To further verify the effectiveness of this invention, the continuous system of this invention was compared with a traditional distillation system involving intermittent neutralization in a stirred tank, jacketless preheating, and forced circulation filtration. The results showed that, at the same processing scale, the system of this invention achieved continuous and stable operation for over 720 hours without shutdown for cleaning, while the traditional system required shutdown for cleaning every 168 hours on average due to reboiler blockage. Simultaneously, the overall steam energy consumption of the system of this invention was reduced by approximately 20%-30% compared to the traditional process. This fully demonstrates the significant superiority of this invention in system integration design.

[0034] In summary, the specific embodiments described above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made based on the technical solutions of the present invention and utilizing the description and drawings of the present invention, or direct / indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A continuous system for recovering triethylamine hydrochloride using calcium oxide, characterized in that, include: Triethylamine hydrochloride preparation vessel (1) is used to prepare a solution of triethylamine hydrochloride and water; Calcium oxide slurry preparation vessel (2) is used to prepare calcium oxide and water into a slurry; The static mixer (3) is provided with two mixing chambers and an external jacket. The two feed ports of the static mixer (3) are respectively connected to the triethylamine hydrochloride preparation vessel (1) and the calcium oxide slurry preparation vessel (2) through a delivery pump. This is used to make the solution and slurry undergo a neutralization reaction in the first mixing chamber and to deeply release triethylamine in the second mixing chamber. The neutralization liquid intermediate tank (4) is connected to the outlet of the static mixer (3); The distillation column (5) has its inlet connected to the outlet of the neutralization intermediate tank (4); A reboiler (6) is connected to the bottom of the distillation column (5) to provide heat load; Forced circulation pump (7) has its inlet connected to the bottom of the distillation column (5) and its outlet is divided into two paths. One path returns to the inlet of the distillation column (5) to form a high-speed flushing circulation, and the other path is connected to the calcium chloride mother liquor storage tank (12). An online self-cleaning filter (8) is installed on the circulation pipeline of the forced circulation pump (7) to remove precipitated salt particles in real time; A vapor phase condenser (9) is connected to the vapor phase outlet at the top of the distillation column (5); The reflux tank (10) is connected to the condensate outlet of the gas phase condenser (9), its reflux port is connected to the top of the distillation column (5), and its outlet is connected to the crude triethylamine storage tank (11). The heat medium inlet of the outer jacket of the static mixer (3) is connected to the top vapor outlet of the distillation column (5) for preheating the feed using the top vapor.

2. The system as described in claim 1, characterized in that, The first stage mixing chamber of the static mixer (3) is equipped with a pH detection port, and the pH value of the material after reaction is maintained at 9-11 by adjusting the flow rate of the feed pump.

3. The system as described in claim 1, characterized in that, The distillation column (5) is equipped with an anti-clogging guide floating valve tray with an opening ratio of ≥12% and an anti-dead zone structure.

4. The system as described in claim 1, characterized in that, The distillation column (5) operates under normal pressure, with the bottom temperature controlled at 100-110℃ and the top temperature controlled at 90-100℃.

5. The system as described in claim 1, characterized in that, It also includes a DCS control system. Temperature sensors and pH sensors are provided at the outlet of the triethylamine hydrochloride preparation vessel (1), the static mixer (3), and the bottom of the distillation column (5). The DCS control system automatically regulates each delivery pump and valve according to the sensor signals.

6. The system as described in claim 1, characterized in that, The calcium oxide slurry kettle (2) is equipped with an airflow conveying device for conveying calcium oxide powder into the kettle in a closed manner.

7. The system as described in claim 1, characterized in that, The calcium chloride mother liquor storage tank (12) is equipped with a basket filter (13) on the inlet pipe for filtering the extracted calcium chloride mother liquor.

8. The system as described in claim 1, characterized in that, The gas phase condenser (9) uses circulating water to provide the refrigerant and condenses the gas phase into a liquid.

9. The system as described in claim 1, characterized in that, The outlet of the forced circulation pump (7) is divided into two paths: one path returns to the bottom inlet of the distillation column (5), and the other path connects to the calcium chloride mother liquor storage tank (12).

10. The system as claimed in claim 1, characterized in that, The distillation column (5) is equipped with a filter on the outlet pipeline from the bottom of the column to the calcium chloride mother liquor storage tank (12) to intercept solid impurities in the calcium chloride mother liquor.

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